1. L.-V. Alfhors, Conformal Invariants, Topics in Geometric Function Theory, Series in Higher Maths, McGraw-Hill, 1973.
2. J.-E. Andersson, Best rational approximation to Markov functions, J. Approx. Theory 76 (1994), 219–232.
3. L. Baratchart, V. A. Prokhorov, and E. B. Saff, Best meromorphic approximation of Markov functions on the unit circle, Found. Comput. Math. 1 (2001), 385–416.
4. L. Baratchart, V. A. Prokhorov, and E. B. Saff, On Hankel operators associated with Markov functions, in: Systems, Approximation, Singular Integral Operators and Related Topics, Oper. Theory Adv. Appl., 129, (eds.: A. A. Borichev and N. K. Nikolski), Birkhäuser, Basel, 2001, 57–69.
5. L. Baratchart, H. Stahl, and F. Wielonsky, Asymptotic error estimates for L2 rational best approximants to Markov functions, J. Approx. Theory 108 (2001), 53–96.